Excessive motor load indicator and voltage cut-out device

ABSTRACT

An overload indicator and protector for a three-phase AC motor wherein there are three pairs of bimetallic elements; each pair being incorporated in a switch and in series with a phase lead of the three phase AC voltage source and a motor lead. One of each pair of the bimetallic elements normally maintains its respective switch in a closed position and opens automatically, or bends toward an open condition, due to the heating effects of current passing therethrough when the motor is in an overload condition. The other bimetallic element of each pair is adapted to close a circuit which causes warning indicia to be activated in the event that the current passing therethrough exceeds a predetermined amount less than that required to open the other switch of the bimetallic pair. A circuit is included in the protector which is responsive to the opening, or bending, of the first mentioned of the pair of bimetallic elements which energizes a solenoid which, in turn, simultaneously causes each of said first mentioned bimetallic elements to open in a quick acting movement. A movable catch element mechanically secures a solenoid so that the switches are retained in the open position until the catch element is manually reset. Movement of the solenoid also opens a switch in a further circuit which secures current to the solenoid after it has opened the switches and is held by the catch element. Further indicia means is connected between each of the switches at a ground to indicate that the protector is in a tripped condition, and still further indicia means is provided to show whether voltage is supplied to each electrical phase. The indicia means may be lamps, a buzzer, or bell, or any combination thereof.

United States Patent Moore [451 Sept. 12, 1972 [54] EXCESSIVE MOTOR LOAD INDICATOR AND VOLTAGE CUT-OUT DEVICE Thomas Moore, 8737 Leavitt Road, Elyria, Ohio 44035 221 Filed: March 4,1971

21 Appl. No.: 121,028

Related US. Application Data [63] Continuation-in-part of Ser. No. 74,277, July 22, 1970, which is a continuation-in-part of Ser. No. 773,923, Nov. 6, 1968, Pat. No.

[72] Inventor:

52 user ..3l8/472,317/13, 337/78 511 Int.Cl. ..H02h 7/08 [58] Field of Search ....3l8/47l, 472; 337/38, 78, 44; 317/13, 14, 40

Primary ExaminerBenjamin Dobeck Attorney-Mason, Mason & Albright [5 7] ABSTRACT An overload indicator and protector for a three-phase 9 pins: MOTOR.

AC motor wherein there are three pairs of bimetallic elements; each pair being incorporated in a switch and in series with a phase lead of the three phase AC voltage source and a motor lead. One of each pair of the bimetallic elements normally maintains its respective switch in a closed position and opens automatically, or bends toward an open condition, due to the heating effects of current passing therethrough when the motor is in an overload condition. The other bimetallic element of each pair is adapted to close a circuit which causes warning indicia to be activated in the event that the current passing therethrough exceeds a predetermined amount less than that required to open the other switch of the bimetallic pair. A circuit is included in the protector which is responsive to the opening, or bending, of the first mentioned of the pair of bimetallic elements which energizes a solenoid which, in turn, simultaneously causes each of said first mentioned bimetallic elements to open in a quick acting movement. A movable catch element mechanically secures a solenoid so that the switches are retained in the open position until the catch element is manually reset. Movement of the solenoid also opens a switch in a further circuit which secures current to the solenoid after it has opened the switches and is held by the catch element. Further indicia means is connected between each of the switches at a ground to indicate that the protector is in a tripped condition, and still further indicia means is provided to show whether voltage is supplied to each electrical phase. The indicia means may be lamps, a buzzer, or bell, or any combination thereof.

3 Claims, 1 Drawing Figure EXCESSIV E MOTOR LOAD INDICATOR AND VOLTAGE CUT-OUT DEVICE CROSS-REFERENCES TO RELATED APPLICATION This is a continuation-in-part of application Ser. No. 74,277 filed Sept. 22, 1970, which, in turn, is a continuation-in-part application of application Ser. No.

773,923 filed Nov. 6, 1968, now US. Pat. No.

conditions, such as may be foundin carwashers, coal mines and steel mills, frequently burn out in spite of conventional electromatically operated overload devices designed to protect them against excessive current conditions. A reason for this is that such .devices permit a motor to operate for an extended period at a load just below that which would activate the conventional circuit breaker whereby eventually the temperature deleteriously affects the insulation. Thus, conventional electromagnetically operated overload protectors, which are practical from the standpoint of not being overly costly, generally afford overload protection for only currents having a level exceeding that which may damage the motor if applied over a prolonged period of time. The problem is not a new one and the fact that it continues to exist strongly indicates that there is and has been for sometime a need for a device in accordance with the invention.

SUMMARY OF THE INVENTION Although overload devices known as thermal overload relays, thermal cut-outs and thermal relays have been known for many years, their utilization has usually involved indirect heating or fusable components. However, I have found that from a practical standpoint, bimetallic elements, when placed in series with an electrical current supplied to motor, have the characteristics of being able to cut-out quickly at high over-- load conditions. Also, they can be set to break circuits effectively, although reacting somewhat more slowly, when continued overload conditions are only slightly above say 10 or percent normal power requirements of the motors. By utilizingthis characteristic in combination with the solenoid which opens all phases of a three phase motor quickly and simultaneously and with lamps and other indicia means, I have provided an overload protector which is particularly useful for three phase motors of the type which now tend to burn out despite the use of conventional electromagnetically operated circuit breakers. The components of the device are inexpensive and long lasting. They are easily mounted and fit within a receptacle of convenient size,

and are adaptable to various adjustments depending upon the specific type of motor and the degree of overload protection desired. I have further found that it is I advantageous to provide in a switch for each electrical phase, two bimetallic elements in series whereby one of the bimetallic elements is finely adjusted to energize indicia means in the presence of any undue overload conditions and the other bimetallic element is utilized to close a circuit which actuates a solenoid to break all three phases when the overload conditions exceed a predetermined amount higher than that required for energizing the warning indicia.

BRIEF DESCRIPTION OF THE DRAWINGS vention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the Figure, the power supply 4 is a 220 volt A.C. three-phase power input which leads into three switches designated generally 5, 6 and 7, via terminals 10a, 11a and 12a, each of which has secured thereto a bimetallic element 14a, 15a, and 16a, respectively. Spaced from opposite ends of the bimetallic elements 14a, 15a, and 16a, are contact members 24a, 25a, and 26a, which are secured to threaded members 30a, 31a and 32a, respectively, which in turn, are threadably received by warning circuit terminals 234, 235 and 236, respectively. Electrical cables 240, 241, 242 connect bimetallic elements 14a, 15a and 16a to intermediate terminals 10b, 11b and 12b, respectively. A bimetallic element 14b, 15b, and 16b, is secured to each intermediate terminal 10b, 11b, and 12b, respectively. Secured to the opposite ends thereof are tappets 40, 41, and 42, which are composed of insulating material of high dielectric characteristics. Opposite tappets 40, 41 and 42 are stationary contact members 44, 45, and 46, and between said tappets and stationary contact members, are movable contact members 50, 51 and 52, respectively. A circuit 54 electrically connects to each of the stationary contact members 44, 45, and 46 to a solenoid 55. The further circuit 56 electrically connects terminal 10a to the movable contact members 50, 51 and 52. Each set of movable contact members and stationary contact members, 50 and 44, 51 and 45, and 52 and 46, are supported by a block 116 of insulating material. Solenoid 55 includes a movable bar member 57 connected to an arm 60 through a lever am 231 which pivots about a stationary pivot member 232. Am 60 includes somewhat enlarged openings 244, 245 and 246, each of which receives one of the bimetallic elements 14b, 15b and 16b, respectively. Thus, when the arm 60 is moved in the direction of arrow 251 by actuation of the solenoid 55 which draws bar member 57 to the left as seen in Fig. 1, bimetallic elements 14b, 15b, and 16b are also moved in the direction of arrow 251 and disengaged from contact members 24b, 25b and 26b, respectively. Bar member 57 is resiliently urged to the position shown in Fig. 1 by means, not shown, in solenoid 55. Contact members 25b, 26b and 27b are secured to threaded members 30b, 31b and 32b which, in turn, are threadably received by motor lead terminals 34, 35 and 36, respectively, which connect to separate phases of a threephase AC motor designated by reference numeral 8.

A catch member, designated generally 271, includes a catch portion 72 and a handle connected by a shaft 272 which is slidably received through openings in stationary brackets and 146. A stop part 147, which may be a cotter pin, holds a helical compression spring 150 in compression against the bracket 146. Catch portion 72 normally bears against a plate member 74 included in movable bar member 57 until, however, the solenoid 55 causes bar member 57 to move to the left (as seen in Fig. 1) whereupon spring 150 urges the catch portion 72 to a position in front of the plate member 74 and thus prevents return of the bar member 57 to the position shown in Fig. 1 until catch member 271 is moved upwardly by handle 135.

Arm 60 carries a depending member 250 which, when arm 50 moves in the direction shown by arrow 251, causes a leaf spring 252 to be disengaged from a contact member 254, leaf spring 252 and contact member 254 being secured to a stationary insulated bracket 255. An electrical line 80 from solenoid 55 connects with a ground lead 81 via the contact member 254 and the leaf spring 252.

An electrical line 260 provides the connection between the terminal 234 and indicia means comprising a yellow lamp 224. In a similar manner, the terminal 235 and indicia means comprising a yellow lamp 225 are connected by an electrical line 261, and the terminal 236 and an indicia means 226, comprising a further yellow lamp, are connected by an electrical line 262. Lamps 224, 225 and 226 are also connected to a grounded circuit 264. In a like manner, the motor lead terminals 34, 35 and 36 are connected to indicia means comprising green lamps 220, 221 and 222 via electrical lines 265, 266 and 267. Green lamps 220, 221 and 222 are also connected to the grounded circuit 264.

It will be noted that the circuit 54 connects with indicia means comprising red lamps 227, three of which are in parallel, and the primary of a step down transformer 230 via solenoid 55. A further electrical line 270 which connects with lamps 227 also connects to the primary of transformer 230. From secondary connection of transformer 230, line 274 connects to a bell 82. The other connection to the secondary of transformer 230 is with grounded circuit 264.

In operation, an excess of current in any bimetallic elements 14a, 15a and 16a causes such element to move to the left, as seen in Fig. 1, whereby electrical contact between the bimetallic element and a contact member 24a, 25a or 26a is made. This, in turn, causes the corresponding lamp 224, 225 or 226 to be energized via the corresponding electrical line 260, 261 or 262. If the condition persists, a warning is conveyed that there is some difficulty in current flow to the threephase motors. The supply of voltage to each of the individual phases of motor 8 via terminals 34, 35 and 36 is indicated by green lights 220, 221, and 222. If a phase failure should occur, the corresponding green lamp will then be extinguished and this may be accompanied by overload indications of the other two phases in the warning lamps connected to the other two phases. For example, if lamp 222 were extinguished this may be accompanied by the energizing of lamps 224 and 225. On the other hand, if the overload condition were due to a bad bearing, one would expect each of the lamps 224, 225 and 226 to be energized while the lamps 220, 221 and 222 remain steady to indicate a normal voltage supply to each of the phases. Accordingly, the on-off pattern of lamps 220, 221, 222, 224, 225 and 226 gives some indication as to the problem involved.

In the event that the overload condition exceeds a predetermined amount, a bimetallic element 14b, 15b or 16b causes its tappet 40, 41 or 42 to move its corresponding movable contact member 50, 51 or 52 to engage the opposed stationary contact member 44, 45 or 46 whereby electrical current from the terminal 10a energizes the solenoid 55 which in turn moves the bar member 57, together with the plate member 74, to the left as seen in Fig. 1 and arm member in the direction of arrow 251 to disengage each contact member 24b, 25b and 26b from the corresponding bimetallic element 14b, 15b and 16b, respectively. Upon plate member 74 so being moved to the left, catch member 271 is caused by the spring to move downwardly in front of the plate member 74 whereby the movable bar member 57 is immobilized until the catch member 271 is restored by moving it upwardly by handle 135. Bar member 57 is then moved by resilient means (not shown) within solenoid 55 back to the position shown in Fig. 1. When the arm 60 moves in the direction of arrow 251 as shown in Fig. 1, the leaf spring 252 is disengaged from the contact member 254 and solenoid 55 is thus de-energized until the arm 60 and the depending member 250 is returned to the position shown in Fig. 1.

It will be seen that when circuit 54 is energized, also the red lamps 227 are energized together with bell 82 via transformer 230 and electrical line 274. The bell 82 continues to ring as long as the circuit 54 is energized.

It will be appreciated that threaded members 30a, 31a, 32a, 30b, 31b, and 32b, provide a fine adjustment to protect the three phase motor 8 from overload conditions as desired.

A backing plate, designated 96 and indicated by dotdash lines, is provided for a receptable not shown. It

will be understood that the backing plate conventionally provides a mounting for the various electrical terminals shown in Fig. 1, the solenoid 55, brackets 145, 146, and 255, pivot member 232, transformer 230, bell 82, and the indicia lamps. However the indicia means may optionally be mounted on a panel removed from the other components. No attempt has been made to describe in detail elements and groups of elements which are conventional and generally widely known to the field to which the invention pertains inasmuch as their exact nature or type is not necessary for understanding and use of the invention by a person skilled in the art. Although the preferred embodiment is described herein of the invention, it will be understood that it is capable of other adaptabilities and modifications within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A device for warning of overload conditions on an electrical three phase AC motor and effecting a complete discontinuance of electrical power to such motor when said motor is overloaded a predetermined amount which comprises:

insulated support means,

three switch means each including a pair of bimetallic elements mounted on said support means,

three circuit means mounted in said support means,

each of said circuit means being connectable to one phase of a three-phase AC source, each said circuit means being in series with a phase of said three-phase AC motor through both bimetallic elements of each said pair of such elements in one of said switches, one of said pair of bimetallic elements in each of said switches being adapted to close a circuit whereby an overload warning indicia means is energized and the other of said bimetallic elements of each of said switches being adapted to close a further circuit connected to disconnect means adapted to disconnect simultaneously the three phases to said motor in response to activation of said disconnect means by any one of said bimetallic elements. 

1. A device for warning of overload conditions on an electrical three phase AC motor and effecting a complete discontinuance of electrical power to such motor when said motor is overloaded a predetermined amount which comprises: insulated support means, three switch means each including a pair of bimetallic elements mounted on said support means, three circuit means mounted in said support means, each of said circuit means being connectable to one phase of a three-phase AC source, each said circuit means being in series with a phase of said three-phase AC motor through both bimetallic elements of each said pair of such elements in one of said switches, one of said pair of bimetallic elements in each of said switches being adapted to close a circuit whereby an overload warning indicia means is energized and the other of said bimetallic elements of each of said switches being adapted to close a further circuit connected to disconnect means adapted to disconnect simultaneously the three phases to said motor in response to activation of said disconnect means by any one of said bimetallic elements.
 2. A device in accordance with claim 1 wherein said disconnect means includes a single solenoid which directly affects the simultaneous disconnection of said phases.
 3. A device in accordance with claim 2 wherein said disconnect means includes catch means operatively connected with said solenoid whereby when said disconnect means is activated, said catch means causes said solenoid to be retained in a position wherein said phases remain disconnected until said catch means is manually reset. 